Utility knives are conventionally formed of two shells that are hollow and are hinged to each other to form a hollow handle. The hinge is usually provided at one end of the two shells while a blade mounting is arranged at the opposite end. The blade mounting holds a knife blade so that it partially protrudes from the handle. The two shells are normally interlocked after a blade has been inserted into the blade mounting so that an unintended opening of the knife is prevented.
The blades are subject to heavy wear and tear and thus must be frequently replaced. It is necessary to open the knife handle for the blade exchange, whereupon the two shells must again be interlocked to form the hollow handle in which spare blades and/or used blades may be stored. The loose storage of blades which are quite sharp, inside the hollow handle may be dangerous, especially when changing a blade. The shells must be opened for a blade changing. In order to open the hollow shells, the shells are conventionally screwed to each other at least at one point away from a hinged connection between the two shells. The hinged connection is so positioned that the blades can be folded away from each other in their longitudinal direction once the screw connection has been released. The screw connection usually includes a threaded hole in one of the shells, while the other shell is provided with a screw having a knurled head rotatably held in a hole in the other shell. By rotating the screw in one or the other direction the shells may be interlocked or released as disclosed in European Patent 0,196,437.
A screw connection provides the desired rigidity of the interlocking of the two shells and the holding of the blades. However, a screw connection once tightened is not necessarily readily releasable even if the screw has a knurled head so that using a tool may become necessary. Additionally, unscrewing the shells from each other and then again screwing the shells together takes time and is not efficient. Moreover, the knurled head of the screw has a tendency to be in the way, either in a plane in the middle between the two shells or on one side of one shell. In both instances the knurled head protrudes outside of the knife handle contour. Thus, the protruding screw head interferes with properly holding the knife, especially when the diameter of the screw head is larger than the cross-sectional width of the shell handle. Such diameter is desirable for operating the screw but not necessarily convenient for handling or rather holding the knife handle. Further, when opening the handle, one must pay attention that the spare blades do not fall out of the shell. Thus, there is room for improvement in such utility knives.